An electrical machine is commonly used by the motor vehicle drive technology sector as a sole drive system or together with a drive motor of a different type (hybrid drive system). Electrical machines are typically used as a drive motor in electric vehicles or hybrid vehicles of this kind. The electrical machine of such a drive train is often regulated in terms of the torque to be delivered. A torque management system receives a torque request on the part of a driver, and generates for a control loop of the electrical machine a target torque (which can be equal to the driver-demanded torque or can be less if, for example, a portion of the demanded torque is to be made available by a combustion engine in a hybrid drive train).
The drive train furthermore generally contains an energy reservoir, for example in the form of a high-voltage battery. The DC voltage made available by the energy reservoir is typically converted, in a power electronics system that contains an inverter, into a plurality of (typically three) phase currents or phase voltages.
The torque delivered by the electrical machine is a function of these phase currents. In order to monitor the torque, of the electrical machine, the phase currents or another variable derived therefrom (such as, e.g., a cross current) is sensed in a control unit. In the context of monitoring, a corresponding fault reaction is triggered when a permissible maximum value of that electrical variable is exceeded. The fault reaction can consist, for example, in an indication for the driver of the motor vehicle, but preferably consists in shutting off the electrical machine. Unintentional triggering of a fault reaction can occur in this context.